1. Field of the Invention
The present invention concerns a directional radiocommunication array comprising a plurality of adjacent radiating elements connected in series by a main line and spaced by one wavelength on said main line. It concerns also a set of such directional arrays.
The invention has a particularly advantageous application in the field of radiocommunication antennas in the UHF band and up into the X band when strong directivity in the plane of the array and weak directivity in the perpendicular plane are required. For example, if the array is disposed vertically the strongly directional plane will be the elevation plane and the perpendicular weakly directional plane will be the azimuth plane.
2. Description of the prior art
One prior art directional radiocommunication array as described above has adjacent radiating elements in the form of four colinear half-wave dipoles energized in series by a main line with an impedance Zc. If ZT is the impedance as seen at the input of the secondary lines connecting the main line to the dipoles, the impedance matching condition at the array input is: EQU Zc=4ZT
which gives Zc=200 .OMEGA. with ZT=50 .OMEGA., the characteristic value for a coaxial line. In this case the main line must be a two-wire line, because of the serial feed. These lines have higher power losses and more importantly radiate a strong interference field. This is one drawback of this prior art directional array, another being related to the problem of implementing the junction or transition between the high-impedance two-wire main line and the low-impedance coaxial secondary lines.
To overcome these drawbacks it is possible to feed the dipoles directly in pairs using dividers by two or a single divider by four. This standard solution has the advantage of simplicity in design and can give satisfactory performance. However, it has high manufacturing (matched symmetrical dipoles with fixing interface to a reflecting mast, for example) and high component costs (numerous cables and connectors, power dividers).
One object of the present invention is to overcome in a simple and inexpensive manner the technical problem of providing a directional radiocommunication array as described above having good radioelectric characteristics and in particular that is free of power losses and radiated interference.